ecret telephony

ABSTRACT

1. In a system of secret transmission of speech, means to subdivide speech waves constituting a message into a plurality of narrow frequency bands, means to integrate the energy in each band, means including a key for determining in successive time intervals a succession of indications unrelated to the speech being transmitted, and transmitting means controlled jointly by the integrated energy from each band and by said indications for transmitting a cipher from which to derive said speech message.



